1. Field of Invention
The invention relates to a method for manufacturing shallow junctions in silicon by implantation of silicon or germanium ions for amorphization of a surface zone, subsequent doping of this surface zone, and finally recrystallization of this surface zone by heat treatment. Furthermore, the invention relates to a semiconductor component containing a shallow junction of this type.
2. Description of the Related Art
To manufacture shallow pn-junctions in silicon, methods are also used whereby surface zones of single-crystal silicon are turned into an amorphous state by implantation of silicon or germanium ions. In a zone pretreated in this way, implanted dopants such as B, BF.sub.2.sup.+, P or As are very narrowly limited with regard to their penetration depth, anomalous (accelerated) diffusion and channeling. A steep dopant profile is the result. During recrystallization of the amorphous surface zone by means of solid-phase epitaxial growth, care must be taken when selecting the temperature so that the dopants do not diffuse too much, in order to retain the dopant profile.
In "J. Appl. Phys." Vol. 54, No. 12, December 1983, pages 6879-6889, a method is described whereby recrystallization takes place at a temperature of 925.degree. C. for a duration of 20 minutes.
In EP 0 201 585, a two-step process for recrystallization of an amorphous surface zone is set forth, whereby the semiconductor specimen is initially held for about 30 minutes at 600.degree. C., the amorphous layer being recrystallized by solid-phase epitaxy (SPE), and then heated within one second to more than 1000.degree. C., as a result of which the implanted dopants are activated.
Both known methods have the drawback that in the recrystallized condition there are defects in the crystalline structure at the point where the interface region from amorphous to crystalline material was situated. These defects are primarily stacking faults and dislocation loops that greatly impair the electrical properties of the junction.
From "IEEE 1990 Bipolar Circuits and Technology Meeting 7.3", pages 162-165, a method is known whereby prior to recrystallization the interface area between the amorphous surface zone and the crystalline base material is smoothed in a temperature process at 450.degree. C. for a duration of 30 minutes. In a subsequent rapid thermal annealing (RTA) process at 1075.degree. C. over 10 seconds, the surface zone recrystallizes and the dopants are activated at the same time. After application of this known method, it was not possible to detect any further defects originating in the interface region, but a more intense boron diffusion had to be accepted in view of the high RTA temperature.